In a construction machine such as a hydraulic excavator, various kinds of fluid (liquid) is used such as the cooling water of a prime mover (an engine and an electric motor), a lubricating oil of a transmission (a transmission oil), and a hydraulic oil of an actuator. When such construction machine is used in an extremely cold region of −40° C. or below, for example, there is a case that, once the prime mover is stopped, such fluid is frozen, and restarting becomes hard. Also, when the prime mover is started in a state the lubricating oil such as the transmission oil is frozen and the lubricating performance thereof is lost, there is a risk of breakage of the transmission, hydraulic pump, actuator and the like.
As a technology for improving the engine starting performance under a cold condition, in PATENT LITERATURE 1 described below, for example, such technology is proposed that a heater is provided in the suction piping that connects a hydraulic pump and a hydraulic oil tank to each other, a hydraulic oil within the suction piping is warmed up before starting an engine, and thereby the starting performance of the engine is improved. Moreover, in PATENT LITERATURE 2 described below, such technology is proposed that preheaters are provided in an engine, a cab, and the like, and the engine, the cab, and the like are preheated by these preheaters. Further, in PATENT LITERATURE 3 described below, such technology is proposed that a hydraulic oil of the entire vehicle body is warmed by driving both of a main electric motor and an electric heater, the main electric motor driving the vehicle body.